Automatic knife sharpening system for forage harvesters

Abstract

In a forage harvester having a motor driven sharpening stone driven back and forth along a path parallel to the axis of a rotating cutterhead to sharpen the knives of the cutterhead, and a door which normally prevents access to the knives, a control circuit is provided for controllig the opening of the door, the movement of the sharpening stone to sharpen the knives, and the closing of the door after the knives have been sharpened. The circuit is controlled by switches located at an operator's control panel and accessible to the operator while he is in the driver's seat of the harvester so that the operator does not have to leave his driving position to accomplish the knife sharpening operation. The circuit includes visual indicators lcoated on the control panel for indicating the status of the circuit during the entire operation. The circuit includes a sensor circuit for sensing the rate of rotation of the cutterhead, the sensor circuit preventing knife sharpening from taking place unless the cutterhead is rotating at a rate greater than the rate required for proper sharpening of the knives.

We claim: 
     
       1. In a forage harvester having a rotatable cutterhead carrying knives, a sharpening stone driven by a sharpener drive motor for sharpening the knives, and an access door which must be opened to permit said sharpening stone to be driven parallel to the axis of rotation of the cutterhead to sharpen the knives, the combination comprising: a bi-directional door drive motor for moving said access door along a path between an open position and a closed position;   switch means having at least a first state and a second state, said switch means being located in a position accessible from an operator's driving position in the forage harvester;   first circuit means responsive to said switch means when it is in said first state for energizing said bi-directional door drive motor to open said access door;   second circuit means responsive to said switch means when it is in said second state for energizing said bi-directional door drive motor to close said access door;   sensor means for sensing when said sharpening stone is in a position in the path of said access door and producing an inhibit signal when the sharpening stone is in the path of said access door;   means for applying said inhibit signal to said second circuit means to thereby inhibit the energizing of said bi-directional door drive motor when the sharpening stone is in the path of the access door.   
     
     
       2. The combination as claimed in claim 1 wherein said first circuit means includes a first switch connected to said switch means and actuated by said access door and a first control circuit connected to said switch means and said first switch for energizing said bidirectional door drive motor to open said access door only when said switch means is in said first state and said first switch is not actuated by said access door. 
     
     
       3. The combination as claimed in claim 2 wherein said second circuit means includes a second switch actuated by said access door when said access door is not fully closed and a second control circuit connected to said switch means and said second switch for energizing said bi-directional door drive motor to close said access door only when said switch means is in said second state and said second switch is actuated by said access door. 
     
     
       4. The combination as claimed in claim 3 wherein said first control circuit includes a relay, said relay having contacts connected in series with said bidirectional door drive motor. 
     
     
       5. The combination as claimed in claim 4 wherein said second control circuit includes a second relay, said second relay having contacts connected in series with said bi-directional door drive motor. 
     
     
       6. The combination as claimed in claim 5 and further comprising a transistor responsive to said inhibit signal for inhibiting the operation of said second relay. 
     
     
       7. The combination as claimed in claim 6 and including a start sharpener switch located in a position accessible from the operator's position in the forage harvester, a timer responsive to actuation of the start sharpener switch for timing an interval during which said sharpener drive motor is energized, and means connecting said timer to said first switch whereby said timer is reset by actuation of said first switch. 
     
     
       8. In a forage harvester having a rotatable cutterhead carrying knives, a sharpening stone driven by a sharpener drive motor for sharpening the knives, and an access door which must be opened to permit said sharpening stone to be driven parallel to the axis of rotation of the cutterhead to sharpen the knives, a method for controlling the movement of the access door and the sharpening stone from the cab of the forage harvester, said method comprising: providing a first and second manually actuated switch means in said cab;   providing a bi-directional drive motor for driving the access door between an open and closed position;   manually actuating said first switch means to energize the bi-directional drive motor to open the access door while inhibiting energization of the sharpener drive motor;   after the access door is fully opened, manually actuating the second switch to energize the sharpener drive motor to drive the sharpening stone for a predetermined interval of time and returning it to a home position; and,   after the sharpening stone has returned to the home position, manually actuating the first switch means to energize the bi-directional drive motor to close the access door while inhibiting energization of the sharpener drive motor.   
     
     
       9. In a forage harvester having a rotatable cutterhead and means for sharpening the cutterhead, an access door which is openable to permit sharpening of the cutterhead, the combination comprising: means for moving said access door along a path between an open position and a closed position;   switch means having at least a first state and a second state;   first circuit means responsive to said switch means when it is in said first state for energizing said means for moving to open said access door;   second circuit means responsive to said switch means when it is in said second state for energizing said means for moving to close said access door;   sensor means for sensing when said means for sharpening is in a position in the path of said access door and producing an inhibit signal when the means for sharpening is in the path of said access door; and,   means for applying said inhibit signal to said second circuit means to thereby inhibit the energizing of said means for moving when the means for sharpening is in the path of the access door.   
     
     
       10. In a forage harvester having a rotatable cutterhead and means for sharpening the cutterhead, an access door which is openable to permit sharpening of the cutterhead, a method for controlling movement of the access door and the means for sharpening, said method comprising: providing first and second manually operable switch means;   providing means for moving the access door between and open and a closed position;   manually actuating said first switch means to energize the means for moving to open the access door while inhibiting energization of the means for sharpening;   after the access door is fully opened, manually actuating the second switch to energize the means for sharpening for a predetermined interval of time and returning it to a home position; and,   after the means for sharpening has returned to the home position, manually actuating the first switch means to energize the means for moving to close the access door while inhibiting energization of the means for sharpening.